Wafer Defect Size Estimation via Dual-System Calibration
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Solution Overview
Problem
Current wafer inspection systems face challenges in increasing throughput and sensitivity while reducing costs, and they struggle to efficiently provide size information about defects on semiconductor wafers.
Innovation Solution
A method involving a monitoring system with higher resolution than the wafer inspection system, using multiple detectors to generate defect detection signals, classifying defects, determining relationships between defect types, sizes, and signals, and generating defect size information using correlation factors and lookup tables to improve defect detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-resolution monitoring system is used to scan wafers and provide defect size information, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The system is divided into two functional segments: a high-resolution monitoring system for calibration and defect characterization, and a lower-resolution wafer inspection system for routine scanning. This segmentation allows each subsystem to be optimized independently, reducing overall system complexity while maintaining measurement precision through the calibration relationship between the two segments.
Solution Approach 2:
Defect size information obtained from the high-resolution monitoring system serves as an intermediary reference that calibrates and enhances the capabilities of the lower-resolution inspection system. This intermediary data allows the inspection system to generate accurate defect size information without requiring equally high resolution hardware.
2Reliability
If multiple detectors are used to generate defect detection signals, then sensitivity and defect detection accuracy are improved, but device complexity increases
Solution Approach 1:
Different detectors are positioned to detect different properties of defects (e.g., scattered light intensity, reflected light patterns). Each detector is optimized for specific local measurement needs, and their combined responses provide comprehensive defect characterization. This allows accurate defect detection without requiring every detector to be equally complex.
Solution Approach 2:
The multiple detectors serve universal functions of detecting various defect types and characteristics through different optical pathways. By designing detectors with multi-functional capabilities to detect different defect properties, the system achieves high reliability without proportionally increasing the number of detector components.
3Measurement precision
If wafer inspection systems are designed to provide detailed defect size information, then measurement precision is improved, but productivity decreases due to increased processing time
Solution Approach 1:
Defect size information is pre-calculated and stored in lookup tables during system calibration using the high-resolution monitoring system. During routine wafer inspection, the lower-resolution system queries these pre-computed tables rather than performing complex real-time calculations, significantly reducing processing time while maintaining measurement precision.
Solution Approach 2:
The system creates a simplified representation or copy of the complex defect characterization data in the form of lookup tables and correlation factors. This copied information can be rapidly retrieved and applied during high-speed wafer inspection without requiring the full computational complexity of the original high-resolution analysis.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the accuracy and efficiency of defect size information generation, enabling more effective defect detection and classification, even with lower-resolution wafer inspection systems, and supports the calibration process for improved inspection tool performance.
Implementation Method 1
Wafer inspection usually includes illuminating a wafer by illumination optics and then collecting and detecting light scattered or reflected from the illuminated wafer
Implementation Method 2
Bright field inspection systems and methods collect light that is reflected (according to Snell's law) from the illuminated wafer
Data Source
AI summary
A method for defect detection includes: (i) scanning at least one wafer by a monitoring system and providing defect size information for each defect that belongs to a group of defects; (ii) scanning the at least one wafer by a wafer inspection system that includes multiple detectors and providing a set of defect detection signals for each defect of the group, wherein the wafer inspection system is characterized by lower resolution than the monitoring system; (iii) classifying the defects to defect classes; (iv) determining multiple relationships between defect types, defect sizes and sets of detection signals; (v) scanning a second wafer by the wafer inspection tool; and (vi) generating, for multiple defects, second wafer defect size information in response to the determined relationships and in response to multiple sets of detection signals generated during the scanning of the second wafer.